U.S. patent application number 09/790208 was filed with the patent office on 2001-10-04 for belt conveyor.
This patent application is currently assigned to Ammeraal International B.V.. Invention is credited to Honeycutt, James Ray, Roet, Simon Jacobus.
Application Number | 20010025769 09/790208 |
Document ID | / |
Family ID | 8171057 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010025769 |
Kind Code |
A1 |
Roet, Simon Jacobus ; et
al. |
October 4, 2001 |
Belt conveyor
Abstract
A belt conveyor comprises a frame wherein at least two support
rolls for supporting a laterally curved endless conveyor belt are
disposed. The laterally curved endless conveyor belt carries on at
least one of its surfaces a guiding bead disposed at or adjacent
the outer peripheral edge thereof. Furthermore the belt conveyor
comprises one or more bearing rolls for bearing the guiding bead.
The guiding bead is a coextruded layered bead comprising a base
layer of a base layer material which is fastened to the conveyor
belt and a top layer of a top layer material which is flexible and
wear resistant. Preferably the base layer is thermoplastically
bonded to a top cover of the conveyor belt. If necessary the base
layer is melted into a supporting bottom fabric of the conveyor
belt. The top layer material comprises preferably a thermoplastic
rubber or copolymer.
Inventors: |
Roet, Simon Jacobus;
(Barsingerhorn, NL) ; Honeycutt, James Ray;
(Grandville, MI) |
Correspondence
Address: |
Michael Best & Friedrich LLP
Suite 700
One South Pinckney Street
Madison
WI
53703
US
|
Assignee: |
Ammeraal International B.V.
Heerhugowaard
NL
|
Family ID: |
8171057 |
Appl. No.: |
09/790208 |
Filed: |
February 21, 2001 |
Current U.S.
Class: |
198/837 ;
198/846; 428/480 |
Current CPC
Class: |
B65G 15/02 20130101;
B65G 15/46 20130101; B65G 2201/06 20130101; Y10T 428/31786
20150401 |
Class at
Publication: |
198/837 ;
198/846; 428/480 |
International
Class: |
B65G 015/60; B32B
027/08 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2000 |
EP |
EP 00200604.7 |
Claims
What is claimed is:
1. A belt conveyor comprising a frame wherein at least two support
rolls for supporting a laterally curved endless conveyor belt are
disposed, the laterally curved endless conveyor belt carrying on at
least one of its surfaces a guiding bead disposed at or adjacent
the outer peripheral edge thereof, and one or more bearing rolls
for bearing the guiding bead wherein the guiding bead is a
coextruded layered bead comprising a base layer of a base layer
material which is fastened to the conveyor belt and a top layer of
a top layer material which is flexible and wear resistant.
2. A belt conveyor according to claim 1, wherein the base layer is
thermoplastically bonded to a top cover of the conveyor belt.
3. A belt conveyor according to claim 1, wherein the base layer is
melted into a supporting bottom fabric of the conveyor belt.
4. A belt conveyor according to claim 1, wherein the base layer
material is a thermoplastic polyester elastomer.
5. A belt conveyor according to claim 1, wherein the top layer
material is a thermoplastic rubber or copolymer.
6. A belt conveyor according to claim 1, wherein the thickness
ratio of the top layer to the base layer in the body of the guiding
bead is at least 2.
7. A belt conveyor according to claim 1, wherein the guiding bead
has an inwardly facing surface, which is inclined with respect to
the surface of the conveyor belt, and which surface is in contact
with a contacting area of a bearing roll.
8. A belt conveyor according to claim 1, wherein the guiding bead
comprises a projection which extends beyond the contacting area of
a bearing roll in the direction of the inner periphery of the
conveyor belt.
9. A guiding bead, obviously intended for a belt conveyor according
to claim 1, wherein the guiding bead is a coextruded layered bead
comprising a base layer of a base layer material which is
fastenable to a conveyor belt and a top layer of a top layer
material which is flexible and wear resistant.
10. A guiding bead according to claim 9, wherein the base layer
material comprises a melt processable rubber or thermoplastic
elastomer.
11. A guiding bead according to claim 9, wherein the base layer
material is a thermoplastic polyester elastomer.
12. A guiding bead according to claims 9, wherein the top layer
material is a thermoplastic rubber or copolymer.
13. A guiding bead according to claim 9, wherein the guiding bead
has a contacting surface, which is inclined with respect to the
base layer of the guiding bead.
14. A guiding bead according to claim 9, wherein the guiding bead
comprises a projection.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a belt conveyor comprising a frame
wherein at least two support rolls for supporting a laterally
curved endless conveyor belt are disposed, the laterally curved
endless conveyor belt carrying on at least one of its surfaces a
guiding bead disposed at or adjacent the outer peripheral edge
thereof, and one or more bearing rolls for bearing the guiding
bead.
BACKGROUND OF THE INVENTION
[0002] Such a belt conveyor is generally known in the art, e.g.
from EP-A-0 566 837. A belt conveyor of this type, also known as a
round belt, is used to carry its load around a curved path, for
example a turn of 90.degree. or even 180.degree.. The guiding bead
has the function to maintain the conveyor belt in its proper
position. In fact the bearing rolls, which are disposed at regular
intervals along the outer circumference of the conveyor belt and
fixed to the frame of the belt conveyor, exert an outwardly
directed force onto the guiding bead.
[0003] In an embodiment of the belt conveyor according to the above
mentioned European patent application 0 566 837 the bearing rolls
comprise a first bearing roll which contacts the inclined inner
face of the guiding bead and a second bearing roll for pressing
against an upper flat surface of the guiding bead. The first
bearing roll is positioned such that it does not contact the upper
surface of the conveyor belt and thus damage to the conveyor belt
is prevented. Information about the bonds between the guiding bead
and the conveyor belt is not provided.
[0004] Several types of guiding beads are known in the art, each
having its own configuration and consequently its own way of
fastening to the conveyor belt. EP-A-0 349 830 discloses a guiding
bead, which in cross-section has a thickened end part provided with
an inwardly and horizontally extending groove limited by said end
part and two horizontal protrusions. The thickened, preferably oval
end part is contacted by two bearing rolls, which are disposed
above and below the conveyor belt at an angle with respect to the
belt surface. This guiding bead is known in the art as the "large
bead". A so-called "small bead" having the thickened part at the
inner end is shown in the drawing of DE-A-23 44 476. Other guiding
beads similar to the large bead are disclosed in JP-A-07/323907,
JP-A-08/081027, JP-A-08/319013 and JP-A-08/319014.
[0005] In practice the guiding beads are glued to the edge of the
belt and then sewn in place. Usually three rows of continuous
stitching through the conveyor belt and the protrusions along the
outside circumference of the belt are used to reinforce the
adhesion properties of the glue. Other fastening means include e.g.
a heat activated adhesive, which is used alone or in combination
with stitching.
[0006] The material most frequently used for the guiding bead is
polyurethane having a durometer from 60 to 70 Shore A. Polyurethane
is tear resistant, tough and reasonably flexible at 70 Shore A.
[0007] When stitching is used, the stitching process actually
weakens the performance of the bead material, such as polyurethane.
The holes, which are punched through the bead during stitching, are
a source of failure, e.g. upon aging the holes may cause stress
fractures in the material. The formation of these stress fractures
or cracks is accelerated during use of the belt conveyor, e.g. by
wear from the bearing rolls, stress applied by belt tension and by
repeatedly flexing over the end pulleys or other supporting rolls.
Once the stress cracks have migrated about 1 mm, they will have
reached the next hole in the bead. This crack propagation occurs
reasonably fast and once several holes have been connected by one
or more cracks, the whole seam begins to fail, in which case the
conveyor belt needs to be replaced by a new one. However, the belt
conveyors of this type are not easily accessible for service and
repair. Furthermore initially a fresh guiding bead usually does not
have a shape, which matches the contacting surface of the bearing
rolls. Thus in the beginning the guiding bead goes through a
so-called wear-in period, during which a significant portion of the
bead is worn off, until the bead conforms to the contacting surface
of the bearing rolls. Because heat is generated in a considerable
amount during this wear-in period, aging, cracking, fracturing and
at last failure are accelerated thereby. Contact between the
stitching and the bearing rolls, for example as a result of
excessive wear in the case of the large bead configuration, should
be avoided, because the stitching will be destroyed almost
immediately. In the case of the small bead configuration contact
between the stitching and the bearing rolls is not possible at all,
and therefore the service life of this type of guiding bead is
improved compared to the large bead configuration. However, a
wear-in period is still present, which has the above-mentioned
drawbacks. The major disadvantage of the small bead configuration
is that the bearing rolls are allowed to contact the upper surface
of the conveyor belt at a position inwardly of the guiding bead,
i.e. just beyond the bead in the direction of the center of the
curve. The bearing rolls will wear away the belt surface as the
belt travels through the return section of the conveyor. This wear
(pattern) together with the cracking of the bead causes failure of
the bead itself, as well as failure of the fastening (adhesion) of
the bead to the conveyor belt. Although the service life of guiding
beads can be increased generally by avoiding stitching, problems
related to the wear-in period will occur.
[0008] In general it can be said that the properties of a guiding
bead, which is manufactured from a single material, are not
sufficient with respect to both wear resistance and adhesion, given
the materials presently employed for the conveyor belt and the
bearing rolls.
[0009] Thus there is an ever continuing need for improving the
guiding beads according to the state of the art in terms of service
life, in particular wear and fastening characteristics.
SUMMARY OF THE INVENTION
[0010] In the belt conveyor of the nature mentioned above according
to the invention the guiding bead is a co-extruded layered bead
comprising a base layer of a base layer material which is fastened
to the conveyor belt and a top layer of a top layer material which
is flexible and wear resistant.
[0011] The use of a co-extruded layered bead according to the
invention allows to select each component of the guiding bead based
upon the demands to which it will be subjected, and thus to
maximize the performance of the guiding bead. In particular it
offers the freedom of selecting the best base layer material for
adhesion to the conveyor belt, and selecting the best top layer
material for flexibility, wear resistance and durability. Thereby
it is possible to avoid the problems associated with the use of a
single material bead according to the state of the art as described
above.
[0012] Other features and advantages of the invention will become
apparent to those skilled in the art upon review of the following
detailed description, claims and drawings in which like numerals
are used to designate like features.
BRIEF DESCRIPTION OF THE DRAWING
[0013] The invention will be further illustrated by means of the
accompanying drawing, wherein:
[0014] FIG. 1 shows a schematic view of an embodiment of a guiding
bead according to the invention; and
[0015] FIG. 2 shows a schematic cross-section of an embodiment of a
belt conveyor according to the invention.
[0016] Before the embodiments of the invention are explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangements
of the components set forth in the following description or
illustrated in the drawings. The invention is capable of other
embodiments and of being practiced or being carried out in various
ways. Also, it is understood that the phraseology and terminology
used herein are for the purpose of description and should not be
regarded as limiting. The use of "including" and "comprising" and
variations thereof herein is meant to encompass the items listed
thereafter and equivalents thereof as well as additional items and
equivalents thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] The selection of the base layer material will depend, among
others, from the type of conveyor belt material to which this base
layer material is to be bonded and the nature of the bonding to be
achieved. Usually the conveyor belt comprises at least a cover
layer made from polyurethane, polyvinylchloride and the like, and a
supporting bottom fabric. Preferably the base layer of the guiding
bead according to the invention is thermoplastically bonded to the
top cover of the conveyor belt. The firm bond thus obtained does
not degrade with use. No adhesive or stitching is required. If the
bottom side of the conveyor belt has to be guided as well,
preferably the base layer material of the guiding bead according to
the invention is melted locally, whereupon some base layer material
flows into the fabric and after curing a firm bond between the
bottom fabric and the bead is established. Suitable base layer
materials comprise melt processable rubbers and thermoplastic
elastomers. A preferred base layer material is a thermoplastic
polyester polymer, e.g. the Hytrel.RTM. grades available from
DuPont. These polyester polymers have a relatively low melt
temperature of approximately 170.degree. C., which allows an easy
application to the bottom fabric of a conveyor belt by melting.
Furthermore it can be thermoplastically bonded to the cover
materials presently employed in conveyor belts of this type such as
polyvinylchloride and polyurethane.
[0018] Preferably the top layer material, which of course is
co-extrudable with the base layer material, is a thermoplastic
rubber or co-polymer. Advantageously the top layer material has a
Shore A hardness in the range of 60-90, more preferably
approximately 70-80. Such a material is tough enough to withstand
the abuse of the application. The hardness and thickness of the top
layer material will be chosen such that the guiding bead as a whole
has sufficient flexibility in the running direction in order to
allow the bead to run over the pulleys of the conveyor without any
significant increase in tension. Lateral flexibility is also
required otherwise the guiding bead can not be bend according to
the curvature (radius) of the conveyor belt. A preferred material
for the top layer is Alcryn.RTM., available from Advanced Polymer
Alloys, which is very well co-extrudable with the Hytrel.RTM.
polyester. This material does not age harden as the polyurethane
materials do. The surface friction characteristic of this material
is sufficient to enable a good grip to the bearing rolls. Other
materials which are co-extrudable with Hytrel.RTM. comprise inter
alia polyvinylchloride, polybutadiene terephthalate and
polyethylene terephthalate.
[0019] If necessary, a suitable intermediate layer may be present
which allows to utilize a base layer material and top layer
material which are not normally considered to be directly
compatible with each other.
[0020] The co-extrudate may comprise usual additives, such as
discoloring antioxidants, fillers, provided that the functional
properties of each of the layers of the guiding bead according to
the invention are not adversely effected.
[0021] In order to distribute the forces which occur during bending
around pulleys it is preferred that the thickness ratio of the top
layer to the base layer in the body of the guiding bead is at least
2. Having a thick top layer allows the entire layer to share the
shear stresses through its thickness and thereby placing less
stress on the top surface of the top layer material.
[0022] Advantageously the shape of the bead, in particular the top
layer, is matched to the shape and angle of the bearing surface of
the bearing rolls, such that no initial wear-in occurs. Thereby
excessive generation of heat and aging of the guiding bead are
prevented. Furthermore it is preferred that the shape is such that
the top cover of the conveyor belt is protected from wear due to
contact with the bearing rolls. Such a protection can be provided
by a part of the bead, which extends beyond the bearing roll.
[0023] In a preferred embodiment the guiding bead has an inwardly
facing surface, which is inclined with respect to the surface of
the conveyor belt, and which surface is in contact with a
contacting area of a bearing roll. The bead also comprises a
projection which extends beyond the contacting area of a bearing
roll in the direction of the inner periphery of the conveyor
belt.
[0024] Hot air and pressure can be used to apply the guiding bead
to one or both of the conveyor belt surfaces in an accurate and
repeatable way. The top and bottom beads end up in exactly the same
curve relative to the curvature of the conveyor belt. Another
possibility includes the use of HF. The guiding bead may be used
with lacing as it may be skived down to the belt surface on the
leading and trailing edges of the lace joint, thereby avoiding the
need of on-site fabrication. A butt joint--another initial position
for bead failure--, as required by the above small and large bead
configuration at the start and stopping positions, can also be
avoided in the present invention.
[0025] The present invention also relates to a guiding bead,
obviously intended for use in the belt conveyor according to the
invention, as defined in claims 9-14.
[0026] The invention will be further illustrated by means of the
accompanying drawing, wherein:
[0027] FIG. 1 shows a schematic view of an embodiment of a guiding
bead according to the invention; and
[0028] FIG. 2 shows a schematic cross-section of an embodiment of a
belt conveyor according to the invention.
[0029] FIG. 1 shows a guiding bead 10, which comprises a base layer
12 of a thermoplastic elastomer, such as Hytrel.RTM. polyester, and
a top layer 14 of a co-extrudable flexible and wear resistant
material, such as Alcryn.RTM.. The thickness of the top layer 14 in
the body of the bead 10 is considerably higher than the thickness
of the base layer 12 in order to dissipate the forces exerted
during use. The guiding bead 10 has a shape which is adapted to the
bearing surface and angle of the bearing rolls, by which the bead
10 will be engaged during use. This shape will be explained in more
detail hereinafter referring to FIG. 2.
[0030] FIG. 2 shows a belt conveyor, indicated by reference numeral
20. The belt conveyor 20 comprises an endless conveyor belt 22. The
conveyor belt 22 has a supporting bottom fabric 24 and a top cover
26 as is usual in the art. An upper bearing guide 28 is disposed at
the outer periphery of the conveyor belt 22. The base layer 12 of
the upper guiding bead 28 is thermoplastically bonded to the top
cover 26 of the conveyor belt 22. A similar bottom bearing guide 30
is also arranged at the outer periphery of the conveyor belt 22
opposite to the upper bearing guide 28. This bottom bearing guide
30 is attached to the bottom fabric 24 by exposing the base layer
12 to a temperature of approximately the melting point. The melted
base layer material flows into the fabric 24 and forms a bonding
upon cooling. In the embodiment shown a frame 32 of the belt
conveyor 20 includes an U-profile section 34, of which the legs 36
each have an end part 38. The end parts 38 each include an inclined
section 40 and a generally vertical end section 42. The end
sections 42 of the end parts extend in opposite vertical
directions. Bearing rolls 44 are inclinedly arranged with respect
to the horizontal part of the conveyor belt 22 in a manner known
per se. A bearing surface of bearing rolls 44 contacts a contacting
surface 46 (see also FIG. 1) of the top layer 14 of the guiding
bead 10. The top layer 14 has a generally triangular shape. As can
be seen, the contacting surface 46 has been provided with the same
angle as the axis of rotation (indicated by 48) of the bearing
rolls 44. As also can be seen from this FIG. 2, the relatively thin
base layers 12 of the guiding beads 28 and 30 respectively are
approximately parallel to the respective surfaces of the conveyor
belt 22. In order to protect the surfaces of the conveyor belt 22
from wear by the bearing rolls 44 the guiding beads 28 and 30 each
have a small extension 50 directed towards the center of the
curvature of the belt 22, which comprises both of the base and top
layers 12 and 14 for adhesion, respectively wear resistance and
flexibility.
[0031] Variations and modifications of the foregoing are within the
scope of the present invention. It is understood that the invention
disclosed and defined herein extends to all alternative
combinations of two or more of the individual features mentioned or
evident from the text and/or drawings. All of these different
combinations constitute various alternative aspects of the present
invention. The embodiments described herein explain the best modes
known for practicing the invention and will enable others skilled
in the art to utilize the invention. The claims are to be construed
to include alternative embodiments to the extent permitted by the
prior art.
[0032] Various features of the invention are set forth in the
following claims.
* * * * *